1. Field of Invention
The present invention relates to a brake for pinching a composite rim without overheating the rim.
2. Related Prior Art
Referring to FIGS. 4 through 6, there is a conventional brake 90 for a typical composite rim 80.
Referring to FIG. 4, the typical composite rim 80 includes two walls 81 and a bridge 82 formed between the walls 81, thus dividing each of the walls 81 into a first portion within the bridge 82, a second portion beside the bridge 82 and a third portion beyond the bridge 82. A tire 84 is put in a groove 83 defined between the third portions of the walls 81. The brake 90 includes two rockers 91 and two shoes 92 each attached to one of the rockers 91. Each of the rockers 91 defines a slot 911 for allowing the adjustment of the position of the related shoe 92. In each of the shoes 92 a lining 93 partially covers the shoes 92 for contact with one of the walls 81.
Referring to FIGS. 4 and 5, an anchor 94 and screw 95 attach each of the shoes 92 to the related rocker 91. The anchor 94 includes an enlarged head. The anchor 94 is inserted through an aperture in each of the shoes 92 and the slot 911 of the related rocker 91 while the head is left in the shoe 92. The screw 95 is driven in the anchor 94.
Referring to FIG. 6, for braking, a rider indirectly rocks the rockers 91 in order to move the shoes 92 so that the linings 93 pinch the third portions of the walls 81.
However, plenty of problems have been encountered in the use of the brake 90. As described referring to FIG. 6, the braking is done through the linings 93 pinching the third portions of the walls 81. Friction entails heat. The heat makes the temperature of the third portions of the walls 81 rise to a range between 200 and 300 degrees Celsius. The heat makes the temperature of the linings 93 rise above 600 degrees Celsius. As made from epoxy resin with a sustainable temperature (“Tg”) in a range between 130 and 180 degrees Celsius, the third portions of the walls 81 easily become soft at 200 to 300 degrees Celsius. As the groove 83 is defined between the third portions of the walls 81, the third portions of the walls 81 are not supported and can easily be deformed by the linings 93. The rim 80 is deformed and not perfectly circular so that the riding is not smooth. In the worst cases, the rim 80 is twisted.
Such a high temperature generally happens during abrupt braking while riding at high speeds or frequent braking while riding down a hill. In either case, if the walls 81 get soft because of overheating and are deformed from the pinching by the linings 93, the tire 84 will be inadequately clamped by the walls 81, thus entailing leakage of air and endangering the rider.
Furthermore, an anchor 94 must be inserted through a shoe 92 before a lining 93 is put in the shoe 92. This is inconvenient. Moreover, a rider may want to replace the anchor 94 with new one. As the lining 93 blocks the anchor 94, the lining 93 must be removed from the shoe 92 before the anchor 94 can be removed from the shoe 92 and replaced with new one. This is troublesome.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.